Method for forming a thin film and apparatus for the same

ABSTRACT

The film-forming apparatus includes a gas introduction tube for introducing an inert gas into a vacuum chamber, a vapor source and a target, and forms thin film by depositing sputtered particles and evaporated particles on the surface of a substrate, the sputtered particles being liberated by sputtering the target using ion energy of plasma generated around the target while the evaporated particles being obtained by evaporating a vapor source by heating and ionizing evaporated components using the plasma. This apparatus includes a substrate holder for holding the substrate so that its film-forming surface faces the side wall of the vacuum chamber; a rotating table for rotating the substrate holder within the vacuum chamber; a target arranged in the side wall of the vacuum chamber so that its sputtering surface faces the inside of the vacuum chamber; a shield detachably fitted in a through hole formed approximately through the center of the target and having a hollow space therein; a gas introduction tube for introducing the inert gas into the hollow space of the shield; and a vapor source provided in the hollow space near the gas exit of the gas introduction tube. This apparatus is employed in the film-forming method of the present invention.

This application is a division of prior application Ser. No. 09/076,885filed May 13, 1998, pending.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for forming a thin filmprovided with a sputtering target and a vapour source, and a method forproducing a thin film using the apparatus.

Formation of a relatively thick (about 1 μm), uniform film of multiplecomponents should be carried out in a short period of time in order toobtain a film of high precision. For example, Japanese PatentApplication Laid-open No. 94473/1980 (JP-A-55-94473) discloses anion-plating apparatus provided with a sputtering target and a vapoursource to form a multi-component film.

This apparatus, as shown in FIG. 3, comprises a substrate 46 fixedinside a vacuum chamber 41, a vapour source 45 disposed in the lowerpart of the vacuum chamber 41, a target 42 and a sputtering electrode 43each placed between the substrate 46 and the vapour source 45, an anode44 disposed on the side of the vapour source 45, and a hot cathode 47provided on the side of the substrate 46 to generate gas-dischargeplasma. In the vacuum chamber 41 of this apparatus, where gas isintroduced from a gas supply source 48, a film is formed by evaporatingthe vapour source 45 at a constant rate through heating and thenionising the particles of the evaporated components in gas-dischargeplasma, as well as applying a high-frequency magnetic field to thesputtering electrode 43 for sputtering the target 42. The film formed onthe substrate 46 is composed of the evaporated component and thesputtered component.

This ion-plating apparatus, however, fails to produce a uniform film ona large substrate, which is in great demand recently. In the vacuumchamber 41, while the vapour source 45 faces the substrate 46, thetarget 42 is arranged approximately perpendicular to the substrate 46 inthe vicinity thereof. This structure prevents particles sputtered out ofthe target 42 from uniformly reaching the surface of a large substrateto give a uniform layer.

Besides, the substrate 46 and the vapour source 45 are spaced at such adistance that the ionised evaporated particles cannot reach thesubstrate in a short time. This causes degradation of the precision of afilm.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to solve the aboveproblems, specifically by providing a method for forming a uniform andhighly-precise film and an apparatus for the same.

The film-forming method of the present invention comprises the steps ofintroducing an inert gas into a vacuum chamber and depositing, on thesurface of a substrate, sputtered particles liberated by sputtering atarget using ion energy of plasma generated around the target andevaporated particles obtained by evaporating a vapour source by heatingand ionising thus evaporated components using the above plasma, and themethod is characterised in arranging the target in the side wall of thevacuum chamber so that its sputtering surface (the surface to besputtered) faces the inside of the vacuum chamber; conducting sputteringof the target and heating of the vapour source simultaneously orseparately, while introducing the inert gas through a hollow space of ashield which is detachably fitted in a through hole formed approximatelythrough the centre of the target, with keeping the surface of thesubstrate opposite to the sputtering surface of the target; and carryingthus yielded sputtered particles and evaporated particles,simultaneously or separately, to the surface of the substrate with a jetof the inert gas, thereby to form a thin film.

Moreover, the film-forming method of the present invention may usedifferent materials respectively for the target and the vapour source.

Further, the film-forming method of the present invention may comprise aplurality of the targets and the vapour sources and fit the shielddetachably in each target so that the inert gas can be introduced intothe hollow space of the shield.

According to the film-forming method of the above structure, it ispossible to conduct the sputtering step of supplying a voltage to atarget electrode and the vapour source heating step simultaneously orseparately, while ejecting the inert gas through the hollow space of theshield which is fitted approximately in the centre of the target. Owingto a jet of the inert gas, the sputtered particles and the ionisedevaporated particles can reach the substrate in a shorter time, thusuniformly forming a film on the whole surface of the substrate.

A multi-component film can be also formed by preparing the target andthe vapour source of different materials.

Further, arrangement of plural targets and vapour sources is effectiveto form a uniform and highly precise film on a large substrate andplural substrates.

The film-forming apparatus of the present invention, comprising a gasintroduction tube for introducing an inert gas into the vacuum chamber,a vapour source and a target, is employed in the above method forforming a thin film on the substrate by depositing sputtered particlesliberated by sputtering the target using ion energy of plasma generatedaround the target and evaporated particles obtained by evaporating avapour source by heating and ionising thus evaporated components usingthe plasma. The film-forming apparatus is characterised in comprising aholding part for holding the substrate so that its film-forming surfacefaces the side wall of the vacuum chamber, a rotating table for rotatingthe holding part within the vacuum chamber, a target arranged in theside wall of the vacuum chamber with its sputtering surface facing theinside of the vacuum chamber, a shield detachably fitted in a throughhole formed approximately through the centre of the target and having ahollow space therein, a gas introduction tube for introducing the inertgas into the hollow space of the shield, and a vapour source provided inthe hollow space near a gas exit of the inert gas introduction tube.

Moreover, the film-forming apparatus may comprise two vapour sourcesprovided in the hollow space near the gas exit of the inert gasintroduction tube and composed of the same element or more than oneelements, and a change-over switch for selectively supplying power toheat either of the two vapour sources.

Further, the film-forming apparatus may comprise a plurality ofintegrated units, each of which comprises the shield having a hollowspace equipped with the gas introduction tube and the vapour source aswell as the target and arranged in or in the vicinity of the side wallof the vacuum chamber, and may allow the holding part to hold pluralsubstrates.

The film-forming apparatus of the present invention is designed to carryout the aforesaid film-forming method. A uniform and highly precise thinfilm can be formed all over the surface of a substrate, because thesputtered particles and the ionised evaporated particles derived fromthe vapour source near the inert gas exit are both carried with a jet ofthe inert gas onto the substrate, and the film-formation process isconducted with rotating the substrate.

The two vapour sources function as follows: when both vapour sources areof the same element, one is reserved until the other is consumed,whereas vapour sources of different elements can provide amulti-component thin film. The vapour source may also be in boatplate-type or crucible-type. Additionally, the vapour source may be inthe form of a wire or a powder and fed from the outside of the vacuumchamber for a continuous long-time operation. These vapour sources areswitchable to each other, as required, by a change-over switch.

Further, the integrated unit of the vapour source-mounted shield and thetarget facilitates instalment of plural shields and targets. Arrangementof the plural integrated units ensures uniform and highly preciseformation of a thin film not only on a large substrate but also on aplurality of substrates at the same time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic view of the fundamental construction ofthe film-forming apparatus according to one embodiment of the presentinvention;

FIG. 2 illustrates a schematic view of an entire construction of thefilm-forming apparatus according to one embodiment of the presentinvention; and

FIG. 3 shows a construction of a conventional film-forming apparatus.

DETAILED DESCRIPTION OF TEE PREFERRED EMBODIMENTS

Referring to the drawings, embodiments of the present invention arehereinafter described. FIG. 1 illustrates a schematic view of thefundamental construction of a film-forming apparatus of an embodiment ofthe present invention, and FIG. 2 is a schematic view of an entireconstruction of the film-forming apparatus.

A vacuum chamber 1 is connected to a vacuum pump (not shown) whichcreates a vacuum of a predetermined degree in the vacuum chamber 1. Aplurality of first sputtering units 10 and second sputtering units 20are vertically installed respectively on the side wall of the vacuumchamber 1. As shown in FIG. 1, the first sputtering unit 10 comprises acopper target 3 disposed so that its sputtering surface faces the insideof the vacuum chamber 1, a permanent magnet 6 provided outside thevacuum chamber 1 via the target 3 and a target electrode 3a, and a yoke9 mounted in contact with the permanent magnet 6. A cylindrical shield 2is fitted in a through hole formed approximately through the centre ofthe target 3, with one end thereof opening outwardly to form an inclinedportion 2a. The shield 2 is equipped with a gas introduction tube 4 forintroducing an inert gas into the vacuum chamber 1, and two vapoursources 5 filled in vapour source containers 5b placed near a gas exit4a of the gas introduction tube 4. The vapour sources 5 are evaporatedby heating the containers 5b with coils 5a wound around the side wallsthereof. Power is selectively supplied to either of the coils 5a by aswitch 7c. In the embodiment, copper is used as the vapour source. Thevoltage supplied to the target electrode 3a is prepared by superimposinga voltage transmitted from an alternating-current RF power source 8athrough an impedance matching box 7a and a voltage transmitted from adirect voltage source 8b for sputtering connected in series with alow-pass filter circuit 7b.

The second sputtering unit 20 comprises a chromium target 23, and apermanent magnet 26 disposed outside the vacuum chamber 1 via a targetelectrode 23a. Direct current is supplied to the target electrode 23a.

In the vacuum chamber 1, substrates S₁, S₂ are held by substrate holders12, with keeping their film-forming surfaces face-to-face with thetargets 3, 23, respectively. The substrate holders 12 are mounted on arotating table 11 which is driven by a motor (not shown) and rotates inthe vacuum chamber 1.

Now, using the above film-forming apparatus, a thin film (Cr--Cu--Crlayer film) is formed on the surfaces of the substrates S₁, S₂,according to the manner hereinafter disclosed.

The substrates S₁, S₂, as the base for forming thin films, are broughtinto the vacuum chamber 1 from a door (not shown) which is evacuated inadvance to a predetermined degree of vacuum, and mounted on thesubstrate holders 12. Then, the substrate S (hereinafter, S indicatesboth S₁ and S₂) is shifted to a position opposite to the target 23 byrotating the rotating table 11 by a motor. At this position, a voltageis supplied to the target electrode 23a for the sputtering of the target23, whereby Cr particles are deposited on the substrate S to form a Crlayer.

Next, the Cr-layered substrate S is brought opposite to the target 3. Atthis position, while inert Ar gas is introduced into the vacuum chamber1, sputtering of the target 3 is conducted, on the one hand, bysupplying a superimposed voltage composed of a voltage from the RF powersource 8a connected through the matching box 7a to the target electrode3a and a voltage from the direct voltage source 8b connected in serieswith the low-pass filter circuit 7b. Through this process, Cu particlesare liberated and deposited on the substrate S. On the other hand,simultaneously, the vapour source 5 is heated by a voltage supplied froma power source 8c through a terminal 7d to the coil 5a. Then, the Cuparticles evaporated out of the vapour source 5 are thrown towards thesubstrate S with a jet of an inert gas ejected nearby, and depositedthereon. The Cu particles derived from these steps provide a Cu layer,thus giving a thin two-layer Cr--Cu film on the substrate S.

Thereafter, the substrate S is again moved opposite to the target 23. Crparticles are likewise deposited to give a three-layer film ofCr--Cu--Cr.

The present embodiment employs a large-sized substrate as the substrateS. Nevertheless, a thin film obtained herein is uniform and veryprecise. In comparison with the conventional technology, the sputteredparticles and the evaporated particles can cover a larger area as aresult of the vertical arrangement of the plural sputtering units 10, 20on the side wall of the vacuum chamber 1. In addition, introduction ofan inert gas helps these particles reach the substrate S in a short timeand thus ensures the precision of the film.

In the present embodiment, both of the two vapour sources are made ofthe same element (Cu). When one vapour source is consumed, a change-overswitch 7c switches the power supply to the other vapour source, so thatCu particles are evaporated continuously.

The present embodiment is directed to the formation of a Cr--Cu--Crfilm. However, thin films of other compositions are also obtainable inaccordance with the combinations of the target 23, the target 3, and thevapour source 5.

By way of example, the combination of a titanium target 23, a tungstentarget 3 and an aluminium vapour source 5 provides a Ti--Al(W)--Ti film.

The present invention should not be limited to the combined use of thefirst sputtering unit 10 and the second sputtering unit 20, as describedin the above embodiment. Independent use of the first sputtering unit 10can also provide a multi-component thin film. For example, a TiN film isformed by using a first sputtering unit 10 composed of a titanium target3 and a titanium vapour source 5 and ejecting a reactive gas of nitrogenor ammonium. In addition, a Cr--Cu--Cr film is obtainable with theindependent use of first sputtering unit 10 by constituting one vapoursource 5 with chromium and the other with copper and appropriatelyoperating the change-over switch 7c.

When the target 3 and the vapour source 5 are made of differentmaterials, the structure of a multi-component thin film is controlled byconducting the sputtering of the target and the ejection of theevaporated particles at separate timings.

As exemplified above, various film-forming conditions can be achievednot only by proper combination of the target material, vapour sourcematerial and inert gas, but also by proper control of the timing andduration of releasing respective particles.

Incidentally, the positions and directions of the first sputtering units10 and the second sputtering units 20 are not limited to the definitionof the present embodiment. These factors may be arranged to suit thesize and number of the substrate.

Further, the vapour source 5 may be a boat plate-type or crucible-typevapour source. Alternatively, an evaporation material can be fed fromthe outside of the vacuum chamber either in the form of a wire through awire-feeding device or in the form of a powder through a pipe. Thisstructure enables continuous feeding of the evaporation material for along time.

What is claimed is:
 1. An apparatus for forming a thin film whichcomprises a gas introduction tube for introducing an inert gas into avacuum chamber, a vapour source and a target, by depositing sputteredparticles and evaporated particles on the surface of a substrate, thesputtered particles being liberated by sputtering the target using ionenergy of plasma generated around the target while the evaporatedparticles being obtained by evaporating said vapour source by heatingand ionising evaporated particles using the plasma, which ischaracterised by:a holding part for holding the substrate so that afilm-forming surface thereof faces the side wall of the vacuum chamber;a rotating table for rotating the holding part within the vacuumchamber; a target arranged in the side wall of the vacuum chamber sothat a sputtering surface thereof faces the inside of the vacuumchamber; a shield detachably fitted in a through hole formedapproximately through the centre of the target and having a hollow spacetherein; a gas introduction tube for introducing the inert gas into thehollow space of the shield; and a vapour source provided in the hollowspace near a gas exit of the inert gas introduction tube.
 2. Anapparatus for forming a thin film according to claim 1, furthercomprising two vapour sources provided in the hollow space near the gasexit of the gas introduction tube and composed of the same element ordifferent elements from each other, and a change-over switch forselectively supplying power to heat either of the vapour sources.
 3. Anapparatus for forming a thin film according to claim 1 or 2, furthercomprising a plurality of integrated units, each of said unitscomprising the shield having a hollow space equipped with the gasintroduction tube and the vapour source as well as the target, arearranged in or in the vicinity of the side wall of the vacuum chamber,and the holding part having means for holding a plurality of thesubstrates.